The present invention relates to a vehicle following apparatus with a distance measuring function which is able to continuously follow a preceding vehicle in an automatic fashion while successively measuring the distance to the preceding vehicle in an optical manner.
Some typical examples of distance measuring apparatuses are disclosed in Japanese Patent Publication Nos. 63-38085 and 63-46363. The apparatuses disclosed therein commonly have a pair of first and second parallel optical systems having two convex lenses 101, 102 disposed in a horizontally aligned relation at a prescribed distance L away from each other, as shown in FIG. 3. A pair of separate image sensors 103, 104 are horizontally disposed at focuses of the lenses 101, 102 apart their focal distance f from the locations of corresponding lenses 101, 102, respectively, for generating respective image signals to a common signal processor 120. The signal processor 120 successively shifts the image signals from the image sensors 103, 104 and electrically superposes them one over the other, so that the distance R from the lenses 101, 102 to an object 121 is calculated based on the principle of triangulation using the following formula: EQU R=(f.times.L)/d
where d is a shift distance by which the image signals are moved to obtain the best match.
On the other hand, a typical method of following a preceding vehicle as sensed by an image sensor or the like is disclosed in Japanese Patent Publication No. 60-33352. In this method, for the purpose of following a target on a display screen, a driver has to set on the display screen a following gate or window which encloses the target to be followed, while looking at the screen.
With the conventional distance measuring apparatuses as described above in which the entire images as sensed by the right and left image sensors 101, 102 are compared with each other for measuring the distance to a preceding vehicle, it is rather difficult to accurately determine the image of the preceding vehicle among various images sensed by the image sensors 101, 102 and hence it is difficult to perform accurate distance detection due to great influences of the background images around the sensed vehicle image.
In addition, the background images around the image of the preceding vehicle are generally complicated and hence it is impossible to automatically discern and follow the preceding vehicle, so the driver is required to successively form a vehicle following window of a desired configuration on the screen of a display on a manual mode. Such an operation of the driver considerably reduces the safety in driving.